private void registerSTV(String source,
String target,
String variant) {
// assert(source.length() > 0);
// assert(target.length() > 0);
CaseInsensitiveString cisrc = new CaseInsensitiveString(source);
CaseInsensitiveString citrg = new CaseInsensitiveString(target);
CaseInsensitiveString civar = new CaseInsensitiveString(variant);
Hashtable<CaseInsensitiveString, Vector<CaseInsensitiveString>> targets = specDAG.get(cisrc);
if (targets == null) {
targets = new Hashtable<CaseInsensitiveString, Vector<CaseInsensitiveString>>();
specDAG.put(cisrc, targets);
}